Reactivity of patient-derived IgG antibodies and monoclonal antibodies 4F3 and 2B2 toward the different domain deletion mutants of β2-GPI. Domain deletion mutants of β2-GPI were coated onto an ELISA plate to test the domain specificity of patient-derived type A IgG fractions (A) and patient-derived type B IgG fractions (B). The patient-derived IgG fractions and monoclonal antibody 4F3 and monoclonal antibody 2B2 were incubated to the plates. Subsequently, the plates were washed and incubated with alkaline-phosphatase-labeled goat anti-human IgG Abs to detect the bound patient IgG antibodies. Staining was performed by using PnPP. The coloring reaction was stopped by 2.4 M NaOH, and absorbance was measured at 405 nm. The obtained optical density was corrected for the optical density obtained with total IgG isolated from pooled plasma from 40 healthy volunteers (panels A and B: OD, 0.101). Error bars represent mean ± SEM of triplicate points.
